Lower Urinary Tract Symptoms (LUTS) such as urinary frequency, urgency, nocturia, and diminished or interrupted urine flow (sometimes termed “weak stream”) are suggestive of urethral obstruction caused by Benign Prostatic Hyperplasia (BPH). Other lower urinary tract disorders (e.g., bladder dysfunction), however, may present with the same symptoms. Unfortunately, the non-invasive diagnostic tests recommended by the American Urological Association (AUA), including the patient self-report scale (e.g., the AUA symptom index) and simple office uroflowmeters that measure flow rate during urination are unable to accurately determine the source of LUTS, especially whether the symptoms are caused by blockage of the urethra due to BPH, or from bladder weakness or some other lower urinary tract condition. A depiction of the lower urinary tract is provided in FIG. 58 attached hereto.
The causes of LUTS are not self-evident. Either a weak bladder (e.g., neurologic damage) or urethral obstruction (e.g., BPH) can cause “weak stream.” Statistically, in men obstruction is twice as likely as poor bladder pressure, so if a trial on medication is not effective, diagnostic/therapeutic prostate surgery is performed. Surgery helps 2 out of 3 patients. However, about 1 in 3 is not helped, and overall about 1 in 20 has some significant side effect from the procedure. Many dollars are spent each year on unneeded prostate procedures and also on the cost of managing adverse effects of the unnecessary surgery.
Some procedures, such as urodynamic studies, can diagnose bladder dysfunction, but are not recommended by the AUA because they are invasive (they involve placement of catheters in the urethra and bladder), and therefore are associated with a significant rate of trauma, infection and other complications. Further, these invasive urodynamic procedures require complex equipment and skilled personnel, and are expensive and uncomfortable for the patient, and cannot be conveniently repeated to confirm abnormal findings or to evaluate response to treatment.
By age 65 many men have enlarged prostates and eventually about one third undergo prostate surgery, mostly for management of symptoms thought to be caused by urethral blockage secondary to BPH, otherwise known as bladder outlet obstruction (BOO). But after surgery many men continue to experience the same LUTS plus additional problems (such as erectile dysfunction and loss of sphincter control secondary to surgical injury). Although more than $3 billion is spent each year in the U.S. for prostate surgery (mostly for BPH), one in three surgical procedures for BPH does not result in relief of LUTS because the urinary tract symptoms initially attributed to BPH were caused by factors other than urethral obstruction.
The expense and risk of existing invasive urodynamic methods make it impractical to perform pre- and post-operative studies to identify bladder dysfunction and objectively measure response to treatment. Although uroflowmetry is presently considered a suitable noninvasive test for detecting lower urinary tract dysfunction, the test does not determine the cause of the dysfunction or specify a “cutoff” flow value that can be used to determine what therapy is appropriate.
In one prospective blind study of uroflowmetry on patients undergoing prostate surgery for LUTS, those patients with peak flow rates above 15 ml/s had significantly less symptom relief from prostate surgery, suggesting that in patients with flow rates above 15 ml/s it is unlikely that obstruction due to BPH is the source of the LUTS. The findings indicate that for many patients urinary tract symptoms are not due to urethral obstruction, but instead involve dysfunction of the bladder. Other studies have shown that uroflowmetry results were not helpful in diagnosing obstruction due to BPH. Thus, the focus on uroflowmetry places an emphasis on a single non-invasive test of questionable diagnostic specificity. Also, nearly all commercially available urodynamic tests that measure bladder function are invasive, and current invasive urodynamic studies also have a poor risk to benefit quotient due to cost and potential complications. Existing non-invasive techniques to measure isovolumetric (i.e., maximum or asymptotic) bladder pressure during urination—such as an inflatable cuff attached to the penis—are inaccurate, painful and also difficult to use in a consistent manner. Accordingly, there is a long-felt need for an accurate, simple, safe, painless, low-cost, and non-invasive technology to determine the source of lower urinary tract symptoms.